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CPE-009 · synthetic case B12-FX-13
Nitrous oxide exposure with neuropathy and a B12 of 310
A normal-looking serum level.
Purpose: A normal-looking serum level.
Inputs the engine received
Laboratory
- Serum vitamin B12
- 310 pg/mL
Patient
- Age
- 27 years
- Sex
- Male
Neurologic features
- Peripheral neuropathy symptoms
- Yes
Drugs, diet and risk groups
- Nitrous oxide exposure
- Yes
What the engine reports
Neurologic involvement can occur without anemia and raises the urgency of finding vitamin B12 deficiency. BSH advises that treatment should not wait for confirmation when neurologic involvement is present.
Detected clinical pattern
B12 Not Low on the Value Entered
Serum B12 is above 300 pg/mL. If suspicion remains (neurologic features, nitrous oxide), methylmalonic acid can still be informative.
- B12 level: B12 310 pg/mL · above 300
Recommended next steps
For physician consideration. Urgent review always comes first.
- 1Measure B12 (with MMA) promptly.BSH 2014.
Differentials, pitfalls and contradicting signals
- Nitrous oxide inactivates B12 and can cause neurologic injury with a normal serum level; MMA and homocysteine are more informative.
Evidence and rule trace · 2 rules
B12-05Neurologic or psychiatric features with unmeasured or low B12
Inputs: neuropathy symptoms · B12 310 pg/mL · nitrous oxide exposure
Neurologic involvement raises the urgency of finding B12 deficiency.
B12-10Drug exposure that lowers B12
Inputs: nitrous oxide exposure
Drug-associated risk of B12 deficiency.
Evidence
- EV-BSH-2014 · Devalia V, Hamilton MS, Molloy AM; British Committee for Standards in Haematology. Guidelines for the diagnosis and treatment of cobalamin and folate disorders. Br J Haematol. 2014;166(4):496-513.
- EV-STABLER-2013 · Stabler SP. Vitamin B12 deficiency. N Engl J Med. 2013;368(2):149-160.
- EV-ADA-STANDARDS · American Diabetes Association Professional Practice Committee. Standards of Care in Diabetes, section on pharmacologic approaches to glycemic treatment (current edition). Diabetes Care.
Physician adjudication required. Clinical decision support for physician review. This output identifies laboratory patterns and safety considerations. It does not diagnose, find the cause, or select a vitamin product, dose or route. Physician adjudication is required.
Change the values
The same engine, starting from this case. Change any value and watch the pattern and the rule trace react.
Serum B12 level
✓ Below 200 pg/mL
Deficiency pattern
✓ 200 to 300 pg/mL
Borderline: MMA and homocysteine settle it
● Above 300 pg/mL
Deficiency unlikely, not excluded
Laboratory
- <200
- 200–300
- >300
Patient
Neurologic features
Drugs, diet and risk groups
More b12 cases
B12-FX-01
B12 of 150 pg/mL with macrocytic anemia
A 67-year-old with MCV 108.
B12-FX-02
Borderline B12 with raised MMA
B12 260 and MMA 0.52.
B12-FX-03
Borderline B12 and no confirmatory test
B12 250.
B12-FX-04
Macrocytic anemia, folic acid ordered, no B12
A safety situation.
B12-FX-05
Neuropathy, B12 220 and metformin for five years
Neurologic features with a borderline level.
B12-FX-06
Posterior-column signs and spasticity
A pattern compatible with subacute combined degeneration.
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